Experts agree: include omega-3s in your heart-healthy diet; they may help your mind as well. The risk is minimal.

Mental Health Implications

Depression

The prevalence of depression in a society is inversely related to that society's consumption of fish: the more that people eat fish, the healthier the population, both physically and mentally. But studies are split when it comes to proving a link between an individual's consumption of omega-3s and lowered depression. All of the eight sources that discuss omega-3s acknowledge that there is promising evidence for omega-3s in the treatment of depression. Five of those studies recommend omega-3 supplementation for depression. Three studies do not recommend it, saying that the evidence is not conclusive enough.

Bipolar Disorder and Adjunctive Use

The same five sources state that omega-3s may have a mood stabilizing effect and help with short-term symptoms of bipolar disorder, and may be used as an adjunct to psychotropic medications, particularly antidepressants.

Other Mental Health Conditions

Experts are researching potential effects of omega-3s on:

cognitive impairment/dementia

perinatal and postpartum depression

schizophrenia

borderline personality disorder

attention deficit hyperactivity disorder (ADHD)

seasonal affective disorder

violent and impulsive behavior

dyslexia

self-harm

childhood mood disorders

The evidence is slim, but these are additional reasons to consider a heart-healthy diet rich in omega-3s.

This brief summary highlights the material covered in our full analysis on omega-3 fatty acids, available here.

Drug Interactions & Contaminants

Anticoagulants, like aspirin, warfarin, or heparin may interact to increase the risk of bleeding, though clinical evidence does not confirm this.

Blood pressure medication may need to be adjusted.

Contaminants may include mercury, PCBs, and dioxins in predatory fish (predatory fish include tuna, salmon, perch, pike, and swordfish).

Side Effects

May affect blood sugar levels (if concerned, check with your doctor)

May worsen low-density lipoprotein (LDL) aka "bad" cholesterol

May trigger fish allergy

May elevate levels of Vitamins A and D (in commercial supplements only)

May cause hypervitamonosis A in rare cases when fish liver oil is used in high doses.

Side effects and drug interactions are the same as eating fish, and appear minimal. The most likely effect is indigestion, best addressed by taking omega-3s (or fish) with other food and, when taking supplements, taking smaller doses at different times of day rather than taking it all at once. Given the side effects and the likely benefits, the use of omega-3s in pregnancy and breastfeeding and in young children seems reasonable.

Vegetarians, Vegans and Plant Sources

Vegetarian and vegan diets are almost always very low in omega-3s, since fish oil is the most efficient way to obtain omega-3s. Some plant-based supplements are available, but they generally are low in the essential omega-3 elements, EPA and DHA. This requires taking a lot of capsules to get a therapeutic dose.

Conclusion

Promising, but not yet proven. A diet rich in small, non-predatory fish - typically about 2 meals a week - is good for almost everyone. Use of a diet rich in non-predatory fish or fish oil may prevent or moderate both depression or bipolar disorder and may be effective in stabilizing mood and enhancing the effectiveness of conventional anti-depressants. Although the evidence is preliminary, omega-3s may also serve as a neuroprotectant. Other uses being studied may encourage use of omega-3s pending development of evidence to the contrary.

Fish Is Best

Fish oil and other supplements supply omega-3s. But fish also contains vitamins, minerals, other fats, and other substances that may work with the omega-3s to protect the heart and overall health. Moreover, fish (but not fried fish), which is rich in protein and low in saturated fat, can replace less-healthful foods such as red meat. The benefits of fish far outweigh the potential risks from contaminants, especially if you eat it in moderation (two servings a week, about 8 to 12 ounces total, is the base recommendation) and vary the types of fish. Small, shorter-lived fish lower in the food chain, such as sardines and mackerel, accumulate less toxins.

Lake Trout is the highest concentration, at 3% EPA and DHA. Atlantic salmon is almost 2%, but most fish are under 1%, meaning 100 grams of fish for each gram of omega-3s. At that rate, a therapeutic dose of 9.6 grams would take a lot of fish: up to two pounds a day. So if you are taking omega-3s as medicine, supplementation is essential.